1. Field of the Invention
The present general inventive concept generally relates to an array type inkjet printer. More particularly, the present general inventive concept relates to an array type inkjet printer with a multi-pass printing structure and a method for compensating an irregular nozzle defect thereof.
2. Description of the Related Art
An inkjet printer is a printer that performs printing by spraying ink drops through a nozzle onto a printing medium, such as a sheet or a film, in response to a predetermined control signal.
An inkjet printer can be classified into a shuttle type inkjet printer or an array type inkjet printer depending on the driving mode of the printer head during printing.
A shuttle type inkjet printer is provided with a plurality of nozzles arranged in a head in a sub-scanning direction. The shuttle type inkjet printer prints one line while moving the head in a scanning direction and prints another line while moving the head in a sub-scanning direction.
On the other hand, an array type inkjet printer is provided with a nozzle and a sheet, wherein the nozzle is longitudinally arranged along a scanning direction of a head to print lines in a sub-scanning direction one by one while the sheet moves in the sub-scanning direction.
Several thousand nozzles may be formed in the head of the array type inkjet printer depending on the desired resolution or design criteria. For example, if 1200 nozzles are used to print one line, then a total of 4800 (1200×4) nozzles are formed in the head when the printer supports four-color printing using the four colors of CMYK (Cyan, Magenta, Yellow, and Black).
If a dead nozzle occurs in a part of the head of the array type inkjet printer provided with a plurality of nozzles as described above, it adversely affects output images. In this respect, in addition to the method of physically exchanging a head with another one, other methods for compensating a dead nozzle have been suggested.
Recently, a multi-pass printing structure for the array type inkjet printer has been suggested to compensate for the dead nozzle. Hereinafter, a multi-pass printing structure will be briefly described with reference to FIGS. 1 and 2.
FIG. 1 conceptually illustrates a multi-pass printing structure in an array type inkjet printer, FIG. 2 illustrates a four-color multi-pass printing method for compensating a dead nozzle in an array type inkjet printer, and FIG. 3 illustrates a problem caused by irregular discharge characteristics of a nozzle during multi-pass printing.
Referring to FIGS. 1 and 2, if a printing medium 30 is fed in a sub-scanning direction (indicated by the arrow “A”) of a printer head cartridge 10, ink is discharged through a nozzle 12 so that a first pass printing operation (shown leftmost in FIG. 2) is performed and the printing medium 30 is fed back. During the first pass, ink of one of the four colors is discharged.
The printing medium 30, which remains engaged with the head cartridge 10 and a feeding roller 20, horizontally moves at a certain interval, and, hence, a second pass printing operation with a different ink color is performed as illustrated in FIG. 2. Referring to FIG. 1, the arrow A represents a feeding direction of the printing medium 30 as noted before, and an arrow B represents the direction of movement of the feeding roller 20.
As illustrated in FIG. 2, the multi-pass printing operation is repeated for each of the total number of ink colors. Thus, in case of the four-color printing illustrated in FIG. 2, the multi-pass printing operation is repeated four times so that first through fourth pass printing operations are carried out to print the whole image in four colors.
A dead nozzle can be compensated by the aforementioned multi-pass printing manner. However, in case of multi-pass printing, additional technology and cost are required for accurate control of nozzles to accomplish suitable display resolution.
Also, charge characteristics of each nozzle 12 may not be maintained uniformly due to any irregularities in the air flow into an ink chamber or user environment. In other words, although a dead nozzle situation may be remedied via multi-pass printing, an irregular nozzle defect may render the multi-pass printing useless.
For example, a white line C may occur in the printed image as illustrated in FIG. 3 due to a nozzle's irregular charge characteristics. The problem illustrated in FIG. 3 may render it difficult to maintain picture quality of a normal image when an irregular nozzle defect is present in an array type inkjet printer with a multi-pass printing structure.